Even most great movies follow a pretty clear, strict formula, adhering to the tried-and-tested tenets of cinematic storytelling that have prevailed ever since the beginning.
But every so often a film will rip up the rule book, doing something completely radical and unexpected which leaves viewers with no earthly idea of where things are going from that point.
These are the sort of scenes where you can practically feel the nervous tension building in the audience, as everyone wonders quite what the hell the director is going to do next.
And while this envelope-pushing filmmaking can often result in ambitious failures, these 10 films all succeeded by taking the rest of the movie in a wildly unexpected and creative direction.
It goes without saying that only the most confident and singular directors should ever attempt to stray this far from the safety of traditional story structure, but with an inspired story and killer cast, it can end up reaping result that viewers won't ever forget.
These 10 movie scenes spat on cinematic convention, threw the tropes in the garbage, and forged ahead on their own unbeaten paths...
10. Introducing Diane Selwyn - Mulholland Drive
If you're watching any David Lynch movie not called The Elephant Man or The Straight Story, you should be bracing yourself for the inevitable moment when the surrealist filmmaker flips the script and upends everything you thought you knew.
Lynch has never pulled this off better than in Mulholland Drive, an already enigmatic yet luridly compelling mystery-thriller which takes a sharp left-turn in its final half-hour, where Naomi Watts suddenly changes from plucky ingenue Betty Elms into struggling actress Diane Selwyn.
The moment Diane wakes up in the very apartment Betty and Rita (Laura Harring) have been investigating, and another character refers to her as Diane, all bets are off.
The remainder of the film is a nightmarish, ambiguous coda which fans have fiercely dissected ever since and Lynch has largely refused to elaborate upon.
Even for the already free-wheeling standards of the inimitable filmmaker, this was Lynch telling the audience, "You thought the last two hours were weird? You ain't seen nothing yet."